Question

我在代码中使用了Lombok来自动生成Getter和Setter代码，现在我想添加其他个人Annotations并使用它。

例如，我想添加@Exist验证现有密钥列表：

    @Getter    @Setter
public class User {

    private String name;
    private List<Integer> keys;

    public boolean existKeys(Integer key) {
        boolean exist = keys.contains(key);
        return exist;
    }

}

创建Annotation之后，我只需执行以下操作：

@Getter    @Setter
public class User {

    private String name;
    @Exist
    private List<Integer> keys;

}

Answer 1

一般注意事项

如果您已经在使用Lombok，则可以添加自定义Lombok转换注释和处理程序。

使用@Target(FIELD)和@Retention(SOURCE)
创建handler
```
@ProviderFor(JavacAnnotationHandler.class)
public class HandleExists extends JavacAnnotationHandler<Exists>{ ...` 
```
处理您的注释。 Handler类包必须以lombok.前缀开头。如果除了javac之外还需要支持Eclipse等，那么您需要编写更多处理程序来扩展适当的框架类。
在处理程序中覆盖/实现handle()方法，通过AST操作生成所需的代码。

您可以将@Getter实施作为样本：

译注： Getter.java

处理程序： HandleGetter.java

您还可以查看sources其他注释和handlers，了解如何生成特定代码。

您需要在lombok，JDK tools.jar。

一些资源：

lombok-pg项目，其中包含一系列自定义lombok注释的来源，特别是FluentSetter.java，HandleFluentSetter.java / FluentSetterHandler.java
custom transformation
简单annotation example及解释。

注意，这里有一些要考虑的要点

这是一堆非常重要的代码来编写和维护。如果你计划使用5-6次注释，那就不值得了。
您可能需要使用lombok升级更改注释处理器实现。
lombok所依赖的编译器中的漏洞也可能被关闭（然后整个Lombok项目将发生巨大变化或停止存在;在这种情况下，如果你广泛使用Lombok，你将会遇到更严重的问题，即使只是@Getter）。

没有Lombok的更复杂的替代方法是对annotation processing使用标准code generation，但是，AFAIK，您不能更改原始类，必须生成/使用扩展它们的类（除非您{ {3}}作为Lombok或采用像CGLib或ASM这样的代码操作。

龙目岛示例

下面是一些创建自定义Lombok注释的工作代码，我称之为 @Contains 。

它只是javac实现，没有Eclipse等。我想为Eclipse或其他IDE创建类似的处理程序并不困难。

它将生成 fieldName 包含（）成员方法，该方法委派给 fieldName .contains（）。

注意，代码只是快速而肮脏（但工作）的样本。对于生产等级注释，您将需要处理许多边界条件，检查正确的类型，处理Lombok配置等，因为它可以在lombok或lombok-pg库源中观察到。

样本用法

<强> SomeEnity.java

@Getter
@Setter
public class SomeEntity {

    @NonNull
    @Contains
    private Collection<String> fieldOne = new ArrayList<>();

    @NonNull
    @Contains
    private Collection<String> fieldTwo = new ArrayList<>();

}

<强> SomeEntityTest.java

public class SomeEntityTest {

    @Test
    public void test() {
        SomeEntity entity = new SomeEntity();

        Collection<String> test1 = Arrays.asList(new String[] { "1", "2" });
        entity.setFieldOne(test1);
        assertSame(test1, entity.getFieldOne());

        Collection<String> test2 = new HashSet<String>(Arrays.asList(new String[] { "3", "4" }));
        entity.setFieldTwo(test2);
        assertSame(test2, entity.getFieldTwo());

        assertTrue(entity.fieldOneContains("1"));
        assertTrue(entity.fieldOneContains("2"));
        assertFalse(entity.fieldOneContains("3"));
        assertFalse(entity.fieldOneContains("4"));

        assertFalse(entity.fieldTwoContains("1"));
        assertFalse(entity.fieldTwoContains("2"));
        assertTrue(entity.fieldTwoContains("3"));
        assertTrue(entity.fieldTwoContains("4"));

        try {
            entity.setFieldOne(null);
            fail("exception expected");
        } catch (Exception ex) {
        }

        try {
            entity.setFieldTwo(null);
            fail("exception expected");
        } catch (Exception ex) {
        }

    }
}

注释实施

<强> Contains.java

@Target({ElementType.FIELD})
@Retention(RetentionPolicy.SOURCE)
public @interface Contains {
    Class<?>[] types() default {};
    Class<?>[] excludes() default {};
}

<强> HandleContains.java

@ProviderFor(JavacAnnotationHandler.class) 
@HandlerPriority(65536) 
@ResolutionResetNeeded 
public class HandleContains extends JavacAnnotationHandler<Contains> {

    @Override 
    public void handle(AnnotationValues<Contains> annotation, JCAnnotation ast, JavacNode annotationNode) {

        try {
            JavacNode node = annotationNode.up();
            if (node.getKind() != Kind.FIELD) {
                annotationNode.addError("@Contains is allowed only on fields");
                return;
            }
            Name delegateName = annotationNode.toName(node.getName());
            JavacResolution reso = new JavacResolution(annotationNode.getContext());
            JCTree member = node.get();
            if (member.type == null) {
                reso.resolveClassMember(node);
            }
            Type delegateType = member.type;
            if (delegateType instanceof ClassType) {
                ClassType ct = (ClassType) delegateType;
                //TODO validate that this field is a collection type
                // if(!Collection)
                //   annotationNode.addError("@Contains can only be used on collections");
                final String methodName = "contains";
                MethodSig methodSig = getMethodBinding(methodName, ct, annotationNode.getTypesUtil());
                if (methodSig == null) throw new Exception("no method " + methodName + " in " + ct.tsym.name);
                JCMethodDecl methodDecl = createDelegateMethod(methodSig, annotationNode, delegateName);
                injectMethod(node.up(), methodDecl);
            } else {
                annotationNode.addError("@Contains can only use concrete class types");
                return;
            }
        } catch (Exception ex) {
            //ex.printStackTrace();
            annotationNode.addError("@Contains unexpected error: " + ex.getMessage());
        }

    }

    public JCMethodDecl createDelegateMethod(MethodSig sig, JavacNode annotation, Name delegateName) throws TypeNotConvertibleException {

        JavacTreeMaker maker = annotation.getTreeMaker();

        com.sun.tools.javac.util.List<JCAnnotation> annotations;
        if (sig.isDeprecated) {
            annotations = com.sun.tools.javac.util.List.of(maker.Annotation(genJavaLangTypeRef(annotation, "Deprecated"), com.sun.tools.javac.util.List.<JCExpression>nil()));
        } else {
            annotations = com.sun.tools.javac.util.List.nil();
        }

        JCModifiers mods = maker.Modifiers(PUBLIC, annotations);
        JCExpression returnType = JavacResolution.typeToJCTree((Type) sig.type.getReturnType(), annotation.getAst(), true);
        boolean useReturn = sig.type.getReturnType().getKind() != TypeKind.VOID;
        ListBuffer<JCVariableDecl> params = sig.type.getParameterTypes().isEmpty() ? null : new ListBuffer<JCVariableDecl>();
        ListBuffer<JCExpression> args = sig.type.getParameterTypes().isEmpty() ? null : new ListBuffer<JCExpression>();
        ListBuffer<JCExpression> thrown = sig.type.getThrownTypes().isEmpty() ? null : new ListBuffer<JCExpression>();
        ListBuffer<JCTypeParameter> typeParams = sig.type.getTypeVariables().isEmpty() ? null : new ListBuffer<JCTypeParameter>();
        ListBuffer<JCExpression> typeArgs = sig.type.getTypeVariables().isEmpty() ? null : new ListBuffer<JCExpression>();
        Types types = Types.instance(annotation.getContext());

        for (TypeMirror param : sig.type.getTypeVariables()) {
            Name name = ((TypeVar) param).tsym.name;

            ListBuffer<JCExpression> bounds = new ListBuffer<JCExpression>();
            for (Type type : types.getBounds((TypeVar) param)) {
                bounds.append(JavacResolution.typeToJCTree(type, annotation.getAst(), true));
            }

            typeParams.append(maker.TypeParameter(name, bounds.toList()));
            typeArgs.append(maker.Ident(name));
        }

        for (TypeMirror ex : sig.type.getThrownTypes()) {
            thrown.append(JavacResolution.typeToJCTree((Type) ex, annotation.getAst(), true));
        }

        int idx = 0;
        String[] paramNames = sig.getParameterNames();
        boolean varargs = sig.elem.isVarArgs();
        for (TypeMirror param : sig.type.getParameterTypes()) {
            long flags = JavacHandlerUtil.addFinalIfNeeded(Flags.PARAMETER, annotation.getContext());
            JCModifiers paramMods = maker.Modifiers(flags);
            Name name = annotation.toName(paramNames[idx++]);
            if (varargs && idx == paramNames.length) {
                paramMods.flags |= VARARGS;
            }
            params.append(maker.VarDef(paramMods, name, JavacResolution.typeToJCTree((Type) param, annotation.getAst(), true), null));
            args.append(maker.Ident(name));
        }

        JCExpression accessor = maker.Select(maker.Ident(annotation.toName("this")), delegateName);

        JCExpression delegateCall = maker.Apply(toList(typeArgs), maker.Select(accessor, sig.name), toList(args));
        JCStatement body = useReturn ? maker.Return(delegateCall) : maker.Exec(delegateCall);
        JCBlock bodyBlock = maker.Block(0, com.sun.tools.javac.util.List.of(body));
        StringBuilder generatedMethodName = new StringBuilder(delegateName);
        generatedMethodName.append(sig.name.toString());
        generatedMethodName.setCharAt(delegateName.length(), Character.toUpperCase(generatedMethodName.charAt(delegateName.length())));
        return recursiveSetGeneratedBy(maker.MethodDef(mods, annotation.toName(generatedMethodName.toString()), returnType, toList(typeParams), toList(params), toList(thrown), bodyBlock, null), annotation.get(), annotation.getContext());
    }

    public static <T> com.sun.tools.javac.util.List<T> toList(ListBuffer<T> collection) {
        return collection == null ? com.sun.tools.javac.util.List.<T>nil() : collection.toList();
    }

    public static class MethodSig {
        final Name name;
        final ExecutableType type;
        final boolean isDeprecated;
        final ExecutableElement elem;

        MethodSig(Name name, ExecutableType type, boolean isDeprecated, ExecutableElement elem) {
            this.name = name;
            this.type = type;
            this.isDeprecated = isDeprecated;
            this.elem = elem;
        }

        String[] getParameterNames() {
            List<? extends VariableElement> paramList = elem.getParameters();
            String[] paramNames = new String[paramList.size()];
            for (int i = 0; i < paramNames.length; i++) {
                paramNames[i] = paramList.get(i).getSimpleName().toString();
            }
            return paramNames;
        }

        @Override public String toString() {
            return (isDeprecated ? "@Deprecated " : "") + name + " " + type;
        }
    }

    public MethodSig getMethodBinding(String name, ClassType ct, JavacTypes types) {
        MethodSig result = null;
        TypeSymbol tsym = ct.asElement();
        if (tsym == null) throw new IllegalArgumentException("no class");

        for (Symbol member : tsym.getEnclosedElements()) {
            if (member.getKind() != ElementKind.METHOD || !name.equals(member.name.toString())) {
                continue;
            }
            if (member.isStatic()) continue;
            if (member.isConstructor()) continue;
            ExecutableElement exElem = (ExecutableElement) member;
            if (!exElem.getModifiers().contains(Modifier.PUBLIC)) continue;
            ExecutableType methodType = (ExecutableType) types.asMemberOf(ct, member);
            boolean isDeprecated = (member.flags() & DEPRECATED) != 0;
            result = new MethodSig(member.name, methodType, isDeprecated, exElem);
        }
        if (result == null) {
            if (ct.supertype_field instanceof ClassType) {
                result = getMethodBinding(name, (ClassType) ct.supertype_field, types);
            }
            if (result == null) {
                if (ct.interfaces_field != null) {
                    for (Type iface : ct.interfaces_field) {
                        if (iface instanceof ClassType) {
                            result = getMethodBinding(name, (ClassType) iface, types);
                            if (result != null) {
                                break;
                            }
                        }
                    }
                }
            }
        }
        return result;
    }
}

为Lombok创建自定义注释

1 个答案:

一般注意事项

龙目岛示例

样本用法

注释实施